We characterized the dispersal spectra and phenology of 298 vascular plant species of the sandstone plateaus of Colombian Amazonia. Dispersal modes were determined by the morphology of dispersion units, personal observations on fruit consumption, and an extensive literature review. We obtained the number of species per dispersal mode for the sandstone plateaus and for two recognized vegetation types: open-herbaceous vegetation and low forest-shrub vegetation. Dispersal modes were assigned to 295 plant species. Animals dispersed the highest percentage of species (46.6%), while the percentage of autochorous and anemochorous species was 29.4 and 23 percent, respectively. The dispersal spectrum of the low forest-shrub vegetation type, based on the coverage of every species, showed that percentages of anemochorous (40.2%) and zoochorous species (37.8%) were similar. Autochory was the most important seed dispersal mode of the open-herbaceous vegetation (60%). Birds were the principal group of potential dispersers (58.9%) of zoochorous species and reptiles the least important. We found two marked fruiting peaks, one from the end of the dry season to the beginning of the wet season and the second one from the beginning to the middle of the dry season. Our results showed that besides the differences in the vegetation structure and floristic composition between the sandstone plateaus and the adjacent tall forest, there also exist differences in the dispersal spectra and the fruiting rhythms. RESUMENNosotros caracterizamos el espectro de dispersión y la fenología de 298 especies de plantas vasculares de las mesetas de arenisca de la Amazonia colombiana. Los mecanismos de dispersión fueron determinados en base a la morfología de las unidades de dispersión, observaciones personales sobre el consumo de frutos y una exhaustiva revisión de literatura. Obtuvimos el número de especies por mecanismo de dispersión para las mesetas de arenisca y para los tipos de vegetación reconocidos: vegetación herbácea abierta y vegetación arbustiva-boscosa-baja. Los mecanismos de dispersión fueron asignados a 295 especies de plantas. Los animales dispersaron el mayor porcentaje de especies (46.6%), mientras que el porcentaje de especies autocoras y anemocoras fue 29.4 y 23 por ciento, respectivamente. El espectro de dispersión del tipo de vegetación arbustiva-boscosa-baja, basado en la cobertura de cada especie, mostró que los porcentajes de especies anemocoras (40.2%) y zoocoras (37.8%) son muy similares. La autocoria fué el mecanismo de dispersión de semillas más importante de la vegetación herbácea abierta (60%). Las aves fueron el grupo principal de dispersores potenciales (58.9%) de las especies zoocoras, y los reptiles los menos importante. Encontramos dos picos marcados de fructificación, el primero desde el final de la estación seca hasta el inicio de la estación lluviosa, y el segundo desde el inicio hasta mediados de la estación seca. Nuestros resultados muestran que a pesar de las diferencias en la estructura de la vegetación y compos...

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Vascular plant species compositional patterns of the low forest, scrub, and herbaceous vegetation on white sand soils and sandstone substrates were studied at six sandstone plateaus in Colombian Amazonia, by means of a field survey according to the Braun‐Blanquet relevé method. Canonical Correspondence Analysis (CCA) was applied to separate effects of habitat and spatial configurations of the plateaus on species patterns. Also, information on dispersal ability and phytogeographic affinity of species was used to test explanations for between plateau differences. Low trees, shrubs and herbs were the main species recorded in 212 relevés. The main gradients in the species patterns were linked to the spatial configuration of the plateaus. Spatially controlled species patterns were mainly related to soil depth and soil organic matter. The association between phytogeographic affinity and the habitat controlled spatial link of species pointed at insufficient sampling at one plateau. Dispersal ability did not explain the habitat controlled spatially distributed occurrences of plant species. This might indicate a low frequency of local extinctions at the sandstone plateaus, especially of the poorly dispersed species, possibly because plant populations survive fire or drought disturbances in local sheltered places. Space and habitat controlled species patterns at one plateau were quite distinct from patterns at the other plateaus. This might be due to unmeasured habitat factors (e.g. unrecorded soil variation or human disturbance history) or the preferential, surveyor biased sampling procedure.

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